As methods for removing malodor components or harmful components in air, technologies different in action have hitherto been known, such as physical adsorption by activated carbon or zeolite, reactive absorption by reactive compounds, combustion by precious metal-based catalysts, chemical adsorption and decomposition by manganese oxide-based catalysts, degradation by photocatalysts, and oxidatively decomposing catalysts utilizing ozone. Of them, manganese oxide-based catalysts do not use expensive precious metals, do not require accessory equipment such as heating means or ozone generation means, and are economical. Thus, they are adopted in many fields.
Numerous catalysts containing manganese oxide as an active ingredient have been introduced. It has been introduced that as complex oxides composed of manganese and metals, Mn—Fe complex oxides, for example, exhibit a deodorizing action on acetaldehyde in a low temperature region of 50 to 200° C. (see Patent Document 1).
A deodorizing catalyst containing a manganese-iron complex oxide (MnFe2O4) as an active ingredient has been introduced. As a concrete example, a deodorizing catalyst containing a mixture of a Mn—Fe complex oxide (Mn/Fe element ratio is 33:67) and Fe2O3 (notes: the Mn/Fe element ratio of the mixture is explicitly described as 17:83) as an active ingredient is disclosed. It is described that the Mn—Fe complex oxide may be mixed with a manganese oxide to constitute the deodorizing catalyst, but there is no relevant Example, and there is no detailed description of such a catalyst (see Patent Document 2). A prototype of the catalyst composed of the mixture of a Mn—Fe complex oxide and Fe2O3 was built, and its deodorization performance was evaluated. The outcome turned out to be that the deodorization performance was not fully satisfactory.
As a deodorizing catalyst containing manganese oxide and zeolite, a deodorizing catalyst having manganese dioxide and a copper oxide carried on hydrophobic zeolite having a silica/alumina ratio of 100 or more has been shown to exhibit high deodorizing properties even for a high-humidity gas (see Patent Document 3).
A deodorizing catalyst containing active manganese dioxide and high silica zeolite as an active ingredient has been shown to adsorb a malodorous gas derived from sulfur and oxidatively decompose it (see Patent Document 4).
Furthermore, a deodorizing catalyst comprising a powdery manganese oxide and powdery hydrophobic zeolite in mixture has been shown to decompose odor components oxidatively at low temperatures (see Patent Document 5).
A deodorizing catalyst containing a manganese oxide, graphite, and zeolite is disclosed. In this catalyst, the proportion of the zeolite contained is 1 to 1.5 times that of the manganese oxide, and a composition having a Mn—Fe complex oxide mixed with MnO is not described (see Patent Document 6).
A deodorant containing a complex oxide of Mn and a transition metal, which contains potassium (K), concretely, a complex oxide obtained from K2CO3 (5%), CuO (20%) and MnO2 (75%), has been introduced as accelerating the conversion of an aldehyde into a carboxylic acid (see Patent Document 7).